What does "runtime" mean?

This morning I was going through the Elm docs and I came across this line that caused me to pause:

In Elm, commands (Cmd) are how we tell the runtime to execute things that involve side effects.

I understood "runtime" to be the length of time a program took to run, so this sentence confused me. After talking about it with some people from RC, we learned that, depending on the context, "runtime" can mean different things:

"the runtime"/"the runtime environment" = the programming language's own internal code that runs alongside the code you provided, the environment inside of which your program runs

"at runtime" = things that don't happen until your code is running, like the way JS and Python don't always show you syntax errors until you get into the bad function